Flexible abrasive disk



Feb. 7', 1939.

F. MITSCHANG ET AL FLEXIBLE ABRASIVE DISKS 3 Sheets-Sheet l "Filed Feb.19, 1957 mmh S TM w NT W E/R VM m WWW T MW B Feb. 7, 1939. F. -MITSCHANGET AL I 2,146,543

I FLEXIBLE ABRASIVE DISKS Filed Feb. 19, 1937 3 Sheets-Sheet 2 N V ENTORS EM/ TJCHA N6 I FRANK M/ TJCHANG, JOSEPH AND JUL/AMC. WAND R Feb. 7,1939. F. MI'II'SCHANG ET AL 2,146,543

FLEXIBLE ABRASIVE DISKS Filed Feb. 19, 1957 3 Sheets-Shei :5

FIGll FRANK M/TJ HANG J fig fi c fi va C AND JULIAN c. ANDJER.

BY l ATTORfiS.

Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE FLEXIBLE ABRASIVE nrsnware Application February 19, 1937, Serial No. 128,556

Claim.

This invention relates to abrasive wheels, be-

ing particularly concerned with improvements in flexible abrasive wheelsadapted for use in' the finishing of metal parts.

Objects of the invention are to provide a wheel which may be readilyaxially deformed when driven by power means, in order that the abrasivesurfaces upon the wheel may accommodate themselves to the shape of theobject being worked upon; to provide laminated wheels made up of aplurality of abrasive disks such as emery cloth, so forming the disksthat they will have a greater degree of resilience than would obtain ifthe disks were merely circular sheets of the emery cloth.

A further object is to provide an alternative type of abrasive wheel,composed of a plurality of laminated abrasive sheets, which will retainits utility until the sheets have worn to a very small diameter, .thelaminated disks being so arranged as to present a new surface ofabrasive material as the periphery of the wheel wears.

A further object is to provide an alternative form of laminated abrasivewheel, capable of substantial axial deflection, wherein the individualdisks comprising the wheel are substantially radially slotted, saiddisks being interlocked in such a manner that the rotationally leadingedge of each spoke-like projection of a disk is covered by the trailingedge portion of the next adjacent spokelike portion.

The devices of this invention are particularly adapted for use insmoothing formed sheet metal parts where concave depressions, or holes,are formed in the parts. The abrasive wheels are utilized in a portableelectric drill or similar tool for smoothing and polishing the metalsurfaces, and for removing burrs and sharp edges which result on themetal parts from stamping and other forming operations.

Further objects will be apparent from a reading of the subjoinedspecification and claims and from an examination of the accompanyingdrawings, in which similar numbers indicate like parts, and in which:

Fig. 1 is a side elevation of one form of the abrasive wheel of thisinvention;

Fig. 2 is an axial section through thedisk elements of the wheel;

Fig.3 is a plan of the wheel as viewed from the top of Fig. 1, showingthe proper direction of rotation;

Fig. 4 is a view from the bottom of Fig. 1,'

showing the proper direction of rotation;

Figs. 5 and 6 are plans of the two types of component disksc'omprisingthe wheel;

Fig. '1 is an elevation ofa second embodiment of an abrasive wheel;

Fig. 8 is an axial section of the second embodiment, showing its utilityin removing burrs from the edges of a hole punched in sheet metal;

Fig. 9 is an end elevation as viewed from the bottom of Fig. 7;

Fig. 10 is a side elevation of the wheel showin its use in connectionwith removing burrs from a hole punched. in sheet metal;

Fig. 11 is a side elevation, partly in axial section, of a thirdembodiment of the invention; and

Fig. 12 is an elevation as viewed from the bottom of Fig. 11.

Referring firstto Figs. 1 to 6, inclusive, we show an abrasive wheel soconstructed as to have a high degree of flexibility for axialdeformation. It comprises an arbor 45 having a threaded end It and anabutment washer II, upon which, successively, is a large washer it, fourlayers of abrasive disks i9, 20, 2| and 22 in laminated relation, asecond washer is, and a nut 23, the latter serving to clamp the assemblytightly in place against the abutment washer H. The disks 19 to 22,inclusive, are of special and unique form, as shown in Figs. 5 and 6.The disks l9 and 20 serve to provide an abrasive surface facing towardthe shank of the arbor l5, while the disks 2| and 22 provide an abrasivesurface facing away from the shank of the arbor IS. The several disksare formed with radially oifset slots, designated as 23 in Fig. 5 and as24 in Fig. 6. Referring to Fig. 5, the form of disk shown is utilizedfor the disks 20 and 22 of the wheel, while the form of disk showninFig. 6 is utilized for disks I8 and2| of the wheel. The offset slots23 of Fig. 5 are cut so as to advance clockwise from their inner ends,while the slots 24 of the form of disk shown in Fig. 6 advancecounter-clockwise from the slot inner ends. Referring now to Fig. 5, theslots 23 leave interslot portions 25 of abrasive material, each saidportion having an acutely angled corner 26 and an obtusely angled corner21. Now referring to Fig. 6, the slots leave interslot portions 28 ofabrasive material, each having an acutely angled corner 25 and anobtusely angled corner II. To produce the disk combination 2|, 22 ofFig. 3, a disk of Fig. 5 is superimposed upon a disk of Fig. 6, thecorners 28 of the disk 22 being passed beneath the corners 29 of thedisk 22, whereby the corner' 29 and the corner 21 form trailing edges ofabrasive material which overlap portions of the associated disksthereby, eliminating a loose-leading edge for each spoke-like portion ofthe disk, avoiding any tendency for fraying.

To form the disk combination is, it of Fig.4, a disk of Fig. 6 issuperimposed on a disk of Fig. 5, the corners 29 of the disk it beingtucked under the corners 26 of the disk 2E9, the corners 3d and 26 ofrespective disks thereby forming trailing edge portions overlapping theleading edges of the underlying disk portions.

The two disk assemblies of Figs. 3 and 4 are then placed back to backand assembled upon the arbor E5, thus providing opposed abrasive facesfor the abrasive wheel with no sharp leading edge portions of either setof disks exposed'to catch into work which is being smoothed. By virtueof the slots 23 and M5 in the disks, a substantial degree of axialflexibility is given to the wheel, so that the operator, in passing thewheel over work to be smoothed, may tilt the axis of the wheel in anydesired direction and still hold a substantial portion of the wheel incontact with the work, also allowing the wheel to be run into otherwiserelatively inaccessible depressions which may be formed in the work.

The form of abrasive wheel shown in Figs. 7 to 10, inclusive, thoughhaving the same basic features of axial flexibility which obtain in thefirst embodiment, is better adapted for smoothing the burrs from holeswhich may be punched in sheet metal. This wheel comprises a core ofresilient material such as sheet rubber, and designated as it, havingoppositely'facing abrasive disks t! placed on opposite sides thereof.The disks ll with the resilient disk dd, are assembled upon a mandrel Mas by a screw 63, the central portion of the wheel assembly beingreinforced by washers t t. As shown in Fig. 9, the assembly of disks isformed with a circumferential plurality of segmental cutouts 65, thecutouts extending a substantial distance inwardly from the peripherytoward the center of the disk. The extent to which the slots mayapproach the center may vary for different sizes and types of disks, andin accordance with the character of work to be done. Generally, however,the slots should extend inwardly slightly more than half of the radiusof the disk. When the wheel above described is rotated by an electricdrill or other suitable power means, the edge of the wheel has a highdegree of axial flexibility in both directions and, in fact, may be sodeformed as to pass through a hole of substantially less diameter thanthe diameter of the wheel when it is in a planar attitude. Accordingly,Figs. 8 and 9 indicate the wheel being passed downwardly and upwardly,respectively, through an opening td punched in a metal sheet 27, wherebyburrs such as 418 at the edge of the hole are efliciently and promptlysmoothed. The action of a wheel of this type in rounding off the edgesof the opening is very effective for, as the wheel is moved toward theopening, it is in a planar attitude and thus initially smoothes the edgeof the opening substantially in the plane of the sheet M. As the wheelis pressed inwardly, it deforms to smoothly round off the corner of theopening until it issues through the sheet and again assumes a planarattitude. Thereupon, the wheel is pulled upwardly through the sheet, asshown in Fig. 10, to effectively smooth the corners on the .bottomsurface of the sheet. 7

Figs. 11 and 12 showan alternative form of abrasive wheel which is welladapted for use in smoothing depressions formed in fabricated articlesas, for instance, the depressions of aircraft aiaasse cowling. Thiswheel comprises a mandrel 53 provided with an abutment washer 5i and acupped washer 52. An abrasive disk 53 of relatively small diameter isthen assembled on the mandrel, with the abrasive surface facing towardthe mandrel, then a succession of disks 5d of increasing diameter areassembled, each having its abrasive surface toward the mandrel.Thereupon, a plurality of disks of consecutively decreasing diameter,these disks being indicated as 55, are assembled upon the mandrel, thewhole series of laminated disks then being made fast to the mandrel by ascrew 56. The distance from the inner face of the cupped washer 52 tothe end of the mandrel, is made substantially coextensive with thethickness of the stack of disks 53, 5t and 55, so that, when the screw5b is driven home, the central portions of the several disks are forcedto a concave shape in accordance with the contour of the cupped washer52. The resultant wheel assembly provides resilient working faces on thetop, edge, and bottom of the Wheel, so that the latter has greatflexibility in adapting itself to virtually any kind of contour on thework upon which it is used.

Generally speaking, all three embodiments of the abrasive wheels shownhave the common characteristic of being composed of laminated sheets ordisks of conventional abrasive cloth whereby a flexible abrasive wheelobtains. several disks involved in the embodiments of the invention maybe readily fabricated by die-cutting or manually cutting the initialsizes and sheets so that replacements of worn disks may be made in aminimum of time. third embodiments of the invention have the addedadvantage that they may be used until the wheel is worn to very smallsize, due to the fact that, as the laminations wear, they uncover afresh abrasive surface on the next disk, avoiding the necessity ofconstantly replacing abrasive disks. as the disks become frayed, and asthe abrasive material becomes either dull or worn.

While we have described our invention in detail in its present preferredembodiments, it will be obvious to those skilled in the art, afterunderstanding our invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Weaim in the appended claims to cover all such modifications and changes.

What is claimed is:

l. A flexible abrasive wheel comprising a pair of flexible abrasivedisks each having a circumferential plurality of radially offset slotstherein forming ofiset spokes, the spokes of respective disks beinginterlocked to provide an anti-rotational overlap by the spoke trailingedges of respective disks, over the next adjacent spoke leading edges.

2. A flexible abrasive wheel comprising a flexible disk having aplurality of uniformly radially offset slits extending from thecircumference of the disk inwardly, a second disk having slits uniformlyradially offset in opposite sense to the slits of the first disk, saiddisks being coaxial and interlocked, the oppositely oflset spokesthereof, formed by said slits, being at the several slits to provide aplurality of spokes trailing edges each overlapping the leading edge ofthe adjacent spoke. I

3. A flexible abrasive disk for abrading work applied to the disk facecomprising an arbor, a disk thereon having inwardly projecting slotsaround its circumference retreating from the di- The 30 The first and 35rection of rotation forming rotationally retreating strips therearound,a second disk overlying the first disk having inwardly projecting slotsaround its circumference advancing into the direction of rotationforming rotationally advancing strips therearound, the corner of eachrotationally advancing strip being tucked through a slot of the otherdisk in a manner such that all of the trailing edges of the rotationallyadvancing strips cover the leading edges of the rotationally retreatingstrips, and all of the trailing edges of the rotationally retreatingstrips cover the leading edges of the rotationally advancing strips.

4. A flexible abrasive wheel comprising a set of at least two flexibledisks, each having a plurality of slits formed therein to define betweenFRANK MITSCHANG. JOSEPH MITSCHANG. JULIAN C. WANDER.

